The United Nations Special Envoy for Haiti, former U.S. President Bill Clinton, offered the strongest statements to date acknowledging the role U.N. peacekeepers are believed to have played in the deadly outbreak of cholera in quake-ravaged Haiti.

During a tour of a hospital there this week, Clinton was pressed on the U.N.'s role in an outbreak that has killed more than 7,000 Haitians -- a politically-charged topic for more than a year now, with the U.N. repeatedly refusing to accept responsibility for the outbreak despite mounting scientific evidence that international peacekeepers were the most likely culprits.

"I don't know that the person who introduced cholera in Haiti, the U.N. peacekeeper, or [U.N.] soldier from South Asia, was aware that he was carrying the virus," Clinton said, adding that "it was the proximate cause of cholera. That is, he was carrying the cholera strain. It came from his waste stream into the waterways of Haiti, into the bodies of Haitians."

Clinton went on to say that he believes what "really caused" the outbreak was the country's dismal sanitary conditions. "Unless we know that he knew or that they knew, the people that sent him, that he was carrying that virus and therefore that he could cause the amount of death and misery and sickness, I think it's better to focus on fixing it."

Clinton's comments came in response to a question from Ansel Herz, a freelance journalist working on behalf of the Pulitzer Center on Crisis Reporting.

In a statement to ABC News, U.N. spokesperson Kieran Dwyer said, "In relation to former President Clinton's reported remarks to the press this week in Haiti, we note that he emphasized the importance of focusing on improving Haiti's sanitation system and the fact that the United Nations and others are working hard to do this." Dwyer added that in 2011, over three million people received water supplies, water treatment products, water filtering systems and sanitation materials from United Nations agencies and its humanitarian partners.

In January, ABC News reported on compelling scientific evidence suggesting a United Nations peacekeeper from Nepal carried the virulent strain of cholera to a remote village in October 2010, and dumping of raw sewage from the UN encampment sent the disease into a key water supply for Haitians. In addition to killing 7,000 people, more than 500,000 Haitians have been infected in Haiti.

Leading researchers from Harvard Medical School and elsewhere told ABC News that they felt confident they had traced the strain back to Nepal, and that they believe it was carried to Haiti by Nepalese soldiers who came to Haiti to serve as U.N. peacekeepers after the earthquake that ravaged the country on Jan. 12, 2010. Haiti had never seen a case of cholera until the arrival of the peacekeepers, who allegedly failed to maintain sanitary conditions at their base.

"What scares me is that the strain from South Asia has been recognized as more virulent, more capable of causing severe disease, and more transmissible," said John Mekalanos, who chairs the Department of Microbiology and Immunobiology at Harvard Medical School. "These strains are nasty. So far there has been no secondary outbreak. But Haiti now represents a foothold for a particularly dangerous variety of this deadly disease."

The U.N. had previously repeatedly said there exists no conclusive evidence fingering peacekeepers for the outbreak. The international organization has already faced hostility from Haitians who believe peacekeeping troops have abused local residents without consequence. They now face legal action from relatives of victims who have petitioned the U.N. for restitution. And the cholera charge could further hamper the U.N.'s ability to work effectively there, two years after the country was hobbled by the earthquake.

Over the summer, Assistant Secretary General Anthony Banbury told ABC News that the U.N. sincerely wanted to know if it played a part in the outbreak, but independent efforts to answer that question had not succeeded. He said the disease could have just as easily been carried by a backpacker or civilian aid worker.

Banbury said the U.N., through both its peacekeeping mission and its civilian organizations "are working very hard ... to combat the spread of the disease and bring assistance to the people. And that's what's important now."

"The scientists say it can't be determined for certainty where it came from," Banbury said. "So we don't know if it was the U.N. troops or not. That's the bottom line."

Mark Weisbrot, Co-Director of the Center for Economic and Policy Research called Clinton's comments an important first step toward accountability.

"President Clinton's acknowledgement, as a U.N. official, should bring us one step closer to the U.N. taking responsibility for what it has done, and fixing it." Weisbrot said.